Oligomeric perylene diimide non-fullerene acceptors via direct (hetero)arylation cross-coupling reactions

ABSTRACT

Oligomeric compounds useful as organic conjugated materials in electronic devices. Oligomeric compounds contain three or more or four or more of certain PDI units bonded to an organic core. The organic core contains one, two or more thiophene rings. The organic core can contain two or more thiophene rings separated by a linker group; two or more thiophene rings directly fused to each other or indirectly fused to each other through an optionally substituted aromatic or non-aromatic carbocylic ring system or an optionally substituted aromatic heterocyclic or non-aromatic heterocyclic ring system; or each of two or more thiophene rings is fused to an aromatic or non-aromatic carbocylic ring system or an aromatic heterocyclic or non-aromatic heterocyclic ring system and the resulting fused rings containing a thiophene ring are each separated by a linker group M. Methods for making oligomeric compounds by direct heteroarylation are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application62/728,462, filed Sep. 7, 2018, which is incorporated by referenceherein in its entirety.

BACKGROUND

The invention relates to the synthesis of thiophene-based core perylenediimide tetramers, hexamers, octamers or higher oligomers via a uniquedirect heteroarylation (DHA). Certain thiophene-based core structuresare functionalized with four or more perylene diimides at active C—Hpositions in the core. The methods herein provide simple syntheticpathways to tetrameric and higher oligomeric perylene diimides, whichare useful, at least, as electron acceptors for organic solar cells. Theinvention further relates to the PDI tetramers, hexamers, octamers andhigher oligomers that are readily prepared by this new method.

Organic conjugated materials are useful in an array of applicationsranging from photovoltaics to cancer cell imaging.¹⁻³ Interest in thesematerials stems from the ability to alter the chemical structure to finetune materials properties.⁴⁻⁷ In addition, the ability to render organicconjugated materials soluble has led to major advances in the field ofprinted electronics.⁸ The development of practical organic buildingblocks and synthetic methods from which to construct organic materialssuitable for large scale manufacturing is an active area of study.⁹⁻¹¹With respect to the latter, the direct (hetero)arylation (DHA) reactionhas emerged as one of the most useful coupling protocols to make newpolymeric and molecular organic materials in a greener fashion.¹²⁻¹⁵Direct CH bond functionalization eliminates the need for incorporationof directing groups and allows for previously unavailable substrates tobe utilized.

Specifically, for organic materials, their use as active materials inorganic solar cells (OSCs) has been widely studied. In this application,the organic materials harvest the energy of photons, create free chargecarriers and transport charges to electrodes.¹⁷ Within the field ofOSCs, the development of non-fullerene acceptors (NFAs) has been ofsignificant recent interest.¹⁸⁻²³

Two classes of NFAs based upon perylene diimides (PDI) andindancenodithiophene (IDT) building blocks have so far emerged ascandidates for delivering good performance OSCs. The IDT based NFAs havean IDT core flanked with planar, electron withdrawing end caps, with theentire molecule rendered electron accepting.^(24,25) The IDT core isinsulated with bulky side chains and serves to shuttle electrons withinthe molecule, while the endcaps drive self-assembly and facilitateselectron transfer. The molecules typically adopt a very planar geometry.

In contrast, PDI-based NFAs are multi-chromophore in nature and the bestperforming materials have highly twisted geometries to prevent strongaggregation of the PDIs, allowing for appropriate phase separationwithin the active layer films.²⁶⁻²⁸ Many of the better performingmaterials are dimeric in nature, but an emerging trend has been to beconstruct tetrameric PDI NFAs.²⁹⁻³² We note in particular that a fusedring PDI-tetramer (FTTB-PDI4) with PDI units ring-fused to atetrathienylbezene is currently the best performing material to ourknowledge.⁴⁵

U.S. Pat. No. 9,865,819 relates to certain nitrogen annulated perylenediimides useful as electron transport materials in organic electronicdevices. In one aspect, the patent relates to N-annulated PDI compoundsof formula:

where:X is halogen (F, Cl, Br or I), triflyl, tosyl, or mesyl;R₁ and R₂ are independently straight-chain or branched alkyl groupshaving 1-30 carbon atoms; andR₃ is a straight-chain or branched alkyl group having 1-30 carbon atoms.These compounds are at least employed to prepare PDI dimers of formula:

The patent also relates to PDI dimer compounds of formula:

where M is certain divalent linking moieties selected from an arylene, aheteroarylene, an alkynylene, a dialkynlyene, an organic dye or M is and

where M₁ is arylene, a heteroarylene, or an organic dye molecule, and tocompounds of formula:

where:p is 0 or 1, n is 2, 3 or 4, and M₁ is arylene, a heteroarylene, or anorganic dye molecule and M 1 groups do not contain thiophene groups.This patent is incorporated by reference herein in its entirety fordefinitions of groups listed in formulas therein, for methods ofsynthesis of compounds therein as well as for descriptions ofapplications of the PDI compounds and descriptions of electronic devicestherein.

DHA Reactivity with NPDI-Br:

has been extended with various coupling partners includingdiketopyrrolopyrrole^(37,38) (DPP), isoindigo³⁷ (II), thienylisoindigo³⁷ (II-TH), squaraine³⁹, and thieno[3,4-c]pyrrole-4,6-dione(TPD)⁴⁰. The inventors are not aware of any report of using DHA forcouplings with IDT.

PDI and IDT coupling via Stille coupling have been reported previouslyand to require silica-gel column chromatography purification.³⁴⁻³⁶ ThePDI dimer, IDT-2PDI:

was reported prepared in 78% yield by reaction of the trimethyl tin IDTderivative:

with 2× of the PDI starting material:

with Pd(PPh₃)₄ in toluene (110° C.)³⁴. The structurally related PDIdimer:

was reported prepared by an analogous method.³⁵

PDI Dimers of Formula:

where:X is C or N and R₁ is 2-ethylhexyl are reported by Chang et al.³⁶References 34, 35 and 36 are each incorporated by reference herein inits entirety herein for description of methods for characterization ofmaterials and preparation of electronic devices using these materials.

CN107286157 published Oct. 24, 2017 appears to report the synthesis ofcertain PDI tetramers having a core of 3,3′-bithiophene of structure:

where R is various branched alkyl groups. The document also includestetramers of structure:

where:n is 0, 1 or 2; R is an alkyl with 5-30 carbon atoms, R′ is H or analkyl with 1-15 carbon atoms and X is H, CN or alkoxy having 1-10 carbonatoms. Tetramer cores:

are more specifically described therein. This document is incorporatedby reference herein in its entirety for descriptions of varioustetramers and for support for optional exclusion of certain cores fromclaims herein.

This invention extends the DHA coupling method to reaction ofN-annulated PDI derivatives and related PDI derivatives with certainthiophene-based cores, such as IDT, to prepare new N-annulated PDItetrameric, hexameric, octameric and higher oligomeric structures. Theresulting PDI tetramers and higher oligomers function as non-fullereneacceptors providing OSCs with high open-circuit voltages preferablygreater than 1V.

SUMMARY

In one aspect, the invention relates to compounds useful as organicconjugated materials in electronic devices that contain four or more ofcertain PDI units bonded to an organic core. In a specific embodiment,the organic core contains one or more thiophene rings and morepreferably contains two or more thiophene rings. In a specificembodiment, the PDI oligomeric compounds are prepared by directheteroarylation.

In a specific embodiment, the oligomeric compound has the genericstructure I:

where:m is an integer of 4 or higher and more specifically is an integer from4-10, and yet more specifically is 4, 6, 8 or 10;Y is S, Se or N—R₃, where each R₃ in the molecule is independentlyselected from an alkyl, aryl or arylalkyl; andeach R₁ and each R₂ is independently selected from straight-chain orbranched alkyl groups having 1-30 carbon atoms, or more preferably 3-20carbon atoms, or yet more preferably 6-12 carbon atoms.

In a specific embodiment, all PDI moieties in the compound are the same.In a specific embodiment, R₁ and R₂ are alkyl groups having 6-12 carbonatoms and Y is N—R₃, where R₃ is an alkyl group having 6-12 carbonatoms.

In a specific embodiment, m is 4 and the oligomeric compound is a PDItetramer. In a specific embodiment, m is 6 and the oligomeric compoundis a PDI hexamer. Scheme 1B illustrates an exemplary synthesis of a PDItetramer with an IDT core.

In specific embodiments, the oligomeric compounds have four or more PDIgroups therein, each of which is bonded to a core structure containingat least two thiophene rings, wherein:

-   -   (1) the two or more thiophene rings are separated by a linker        group M;    -   (2) the two or more thiophene rings are directly fused to each        other or indirectly fused to each other through an optionally        substituted aromatic or non-aromatic carbocylic ring system or        an optionally substituted aromatic heterocyclic or non-aromatic        heterocyclic ring system; or    -   (3) each of two or more thiophene rings is fused to an aromatic        or non-aromatic carbocylic ring system or an aromatic        heterocyclic or non-aromatic heterocyclic ring system and the        resulting fused rings containing a thiophene ring are each        separated by a linker group M.

The linker M can be a single bond, a double bond, or a divalent ortrivalent linker comprising an alkylene (—(CH₂)_(x)—), an alkenylene(e.g., —CH═CH—), a dialkenylene (e.g., —CH═CH—CH═CH—), an alkynylene(e.g., —C≡C—), a dialkynylene (—C≡C—C≡C—), or an optionally substitutedaromatic or non-aromatic carbocyclic or heterocyclic ring system. Inspecific embodiments, M is an arylene or a heteroarylene. In specificembodiments, M is a moiety as illustrated in Scheme 2.

In specific embodiments, the CORE is a moiety C1-C40 as illustrated inScheme 3, where:

each R₄ is independently selected from H, an alkyl or alkoxy grouphaving 1-30 carbon atoms, an optionally substituted aryl or heteroarylgroup, where optional substitution is substitution with one or morehalogen, CN, alkyl or alkoxy having 1-30 carbon atoms, 1-12 carbonatoms, 3-12 carbon atoms, 6-12 carbon atoms or 1-3 carbon atoms;each R₅ is independently selected from hydrogen, halogen, CN, or alkylor alkoxy having 1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms;each R₆ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms;each R₇ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms; andR_(N) is selected from hydrogen, an alkyl group having 1-30, 1-12, 3-12,6-12 or 1-3 carbon atoms, an aryl group or an arylalkyl group. For CORESof Scheme 3, aryl groups include phenyl and naphthyl groups, amongothers, and arylalkyl groups include benzyl and phenethyl groups.

In specific embodiments, each R₇ is independently hydrogen or halogen oryet more specifically, each R₇ is independently hydrogen or fluorine. Inspecific embodiments, each R_(N) is hydrogen or an alkyl group having1-12 carbon atoms or an alkyl group having 1-3 carbon atoms.

More specifically, the CORE is:

-   -   (a) the moiety C1, C2, C6 or C7;    -   (b) the moiety C3, C4 or C5;    -   (c) the moiety C8, C9 or C35;    -   (d) the moiety C10 or C11;    -   (e) the moiety C12;    -   (f) the moiety C13;    -   (g) the moiety C14, C15 or C16;    -   (h) the moiety C17 or C18;    -   (i) the moiety C19a (Y is C), C19b (Y is P), C19c (Y is N), C19d        (Y is S), C19e (Y is Si), or C19f(Y is Ge);    -   (j) the moiety C19a, C19c or C19d);    -   (k) the moiety C20a, C20b or C20c;    -   (l) the moiety C21, C23 or C24;    -   (m) the moiety C22 or C25;    -   (n) the moiety C26 or C27;    -   (o) the moiety C28 or C29;    -   (p) the moiety C30, C31, C32, or C33;    -   (q) the moiety C34 or C36;    -   (r) the moiety C37;    -   (s) the moiety C38;    -   (t) the moiety C39; or    -   (u) the moiety C40.

The invention additionally relates to an electronic device employing anelectron acceptor wherein the electron acceptor is one or more PDIoligomeric compounds herein. More specifically, the disclosure providesan organic solar cell employing an electron acceptor wherein theelectron acceptor is one or more PDI oligomeric compounds herein. Morespecifically the disclosure provides an organic thin film transistoremploying an electron acceptor wherein the electron acceptor is one ormore PDI oligomeric compounds herein. More specifically, the disclosureprovides a redox flow battery, which comprises one or more PDIoligomeric compounds herein.

In another aspect, the invention relates to a method for makingoligomeric PDI compounds, and more specifically for making PDItetramers, hexamers and higher oligomers. The method reacts a corecarrying 4 or more active C—H bonds with 2 or more equivalents (withrespect to the core) of a PDI precursor and more preferably with 4 ormore equivalents of a PDI precursor in an appropriate solvent in whichthe reactants (core and PDI precursor) are at least partially soluble,in the presence of a palladium catalyst, a proton shuttle and carbonatebase.

The reaction is preferably carried out at a temperature of 70° C. orhigher, dependent at least in part upon the solvent employed, and ispreferably carried out at above ambient room pressure in a sealed vesselunder an inert atmosphere (e.g., N₂). More preferably, the reaction iscarried out at a temperature of 80° C. or higher. More preferably, thereaction is carried out at a temperature of 100° C. of higher. Inspecific embodiments, the precipitated oligomeric reaction product iswashed with appropriate solvent to remove partially reacted products,such as dimers and trimers.

Other aspects of the disclosure will be apparent to one of ordinaryskill in the art in view of the following detailed description andexamples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the proton NMR spectrum of the aromatic region ofIDT-NPDI4.

FIG. 2A illustrates the solution UV-Vis absorption (solid trace) andthin film UV-Vis absorption (dashed trace) of IDT-NPDI4. FIG. 2Billustrates the solution UV-Vis absorption (solid trace) versusflorescence (dotted trace) of IDT-NPDI4. Solution measurements wereperformed in CHCl₃, film was spun cast from 100 μL of a 1% w/v solutionof IDT-NPDI4 in CHCl₃ at 1500 RPM onto a 2×2 cm UV-ozone-cleaned glasssubstrate.

FIGS. 3A and 3B illustrate the optimized structure of IDT-NPDI4 face-on(A) and side-on (B) calculated using DFT at the B3LYP-6-31G(d,p) levelof theory.

FIGS. 4A and 4B illustrate the normalized thin film (CHCl₃) absorptionprofiles of IDT (dotted trace 1), NPDI (dotted trace 2), and IDT-NPDI4(solid trace). FIG. 4A gives structures of IDT, NPDI and IDT-NPDI4. FIG.4B shows the absorption profiles.

FIGS. 5A and 5B illustrate cyclic voltammograms. FIG. 5A shows thesolution cyclic voltammogram of IDT-NPDI4. FIG. 5B shows the solutioncyclic voltammogram of IDT-NPDI4 (solid black traces) with those of thecomponents IDT (dotted trace 1) and NPDI (dotted trace 2).

FIGS. 6A-6D show characterization of OSCs with a PTB7-Th: IDT-NPDI4active layer. FIG. 6A shows current-voltage curves and FIG. 6B showsexternal quantum efficiency of 1:1 blends processed with varying volumepercentage of CN solvent additive. FIGS. 6C and 6D are AFM height andAFM phase images, respectively, of the 1:1 blended PTB7-Th: IDT-NPDI4active layer processed from 10 mg/mL chlorobenzene solution with 5% v/vCN added. Images are 2 μm×2 μm with the surface having an RMS roughnessof 1.36 nm.

FIGS. 7A and B are space charge limited current (SCLC) measurement plotsfor electron and hole mobility, respectively.

DETAILED DESCRIPTION

This invention relates to certain oligomeric PDI compounds in which fouror more PDI units are bonded to a selected organic core, particularly acore containing a thiophene ring and preferably containing two or morethiophene rings. In an exemplary embodiment the oligomeric PDI compoundsof the invention have structure:

where N is the integer number of PDI moieties in the oligomeric compoundand more specifically N is 4 or more and more specifically N is 4-10 andCORE is an organic core carrying N C—H bonds that are active for DHA,such as those in thiophene rings. In specific embodiments, N is 4, 6, 8or 10. In specific embodiments, N is 4. In other embodiments, N is 6.

In specific embodiments, the PDI units are those of formula X:

where:Y is S, Se or N—R₃,R₁ and R₂ are the same or different and are each independently selectedfrom alkyl groups having 1-30 carbon atoms, andR₃ is the same or different from R₁ and R₂ and is selected from alkylgroups having 1-30 carbon atoms.

In embodiments, the PDI precursor is a compound of formula XI:

where X is halogen (F, Cl, Br or I), triflyl, tosyl, or mesyl and othervariables are as in formula X. In a specific embodiment, X is a halogenand in a more specific embodiment, X is Br.

In specific embodiments of formulas X and XI, R₁ and R₂ areindependently selected from a straight-chain alkyl having 10 or morecarbon atoms or a branched chain alkyl having 3 to 20 carbon atoms. Inspecific embodiments, R₁ and R₂ are independently selected from astraight-chain alky having 3 to 9 carbon atoms. In specific embodiments,R₁ and R₂ are independently selected from a branched-chain alky having 3to 10 carbon atoms. In specific embodiments, R₁ and R₂ are the samegroup. In specific embodiments, R₁ and R₂ are selected from branchedalkyl groups of formula —C(Ra)(Rb), where Ra and Rb are, independently,alkyl groups having 2-10 carbon atoms. In specific embodiments, Ra andRb are the same alkyl group. In specific embodiments, Ra and Rb aredifferent alkyl groups. In specific embodiments, Ra and Rb arestraight-chain alkyl groups. In specific embodiments, Ra and Rb arebranched alkyl groups. In specific embodiments, R₁ and R₂ areindependently 1-ethylpropyl, 1-propylbutyl, 1-butylpentyl,1-pentylhexyl, 1-hexylheptyl, 1-heptyloctyl, 1-octylnonyl, 1-nonyldecyl,or 2-ethylhexyl. In specific embodiments, R₁ and R₂ are the same alkylgroup. In specific embodiments, R₁ and R₂ are different alkyl groups. Inspecific embodiments, R₁ and R₂ are both 1-ethylpropyl groups. Inspecific embodiments, R₁ and R₂ are independently selected from branchedalkyl groups having 3-8 carbon atoms. In specific embodiments, R₁ and R₂are the same branched alkyl groups.

In specific embodiments of formulas X and XI, Y is N—R₃.

In specific embodiments of formulas X and XI, Y is S.

In specific embodiments of formulas X and XI, Y is Se.

In specific embodiments of formulas X and XI, R₃ is independentlyselected from a straight chain alkyl having 1 to 12, or 1-10 or 4 to 12or 4 to 10 or 4 to 6 carbon atoms or a branched chain alkyl having 3-12or 3-10 carbon atoms. In specific embodiments, R₃ is independently astraight-chain alkyl group selected from a methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, nonyl, and decyl group. In specificembodiments, R₃ is independently a branched alkyl group having 3-12carbon atoms. In specific embodiments, R₃ is independently a branchedalkyl group having 6-12 carbon atoms. In specific embodiments, R₃ isindependently a branched alkyl group having 3-6 carbon atoms. Inspecific embodiments, R₃ is independently selected from 1-ethylpropyl,1-propyl butyl, and 2-ethylhexyl.

In specific embodiments, the CORE of the oligomer is an organic moietywhich carries 4 or more C—H bonds that are active for direct arylationor direct heteroarylation. For example, C—H bonds of thiophene rings areactive for direct arylation or direct heteroarylation. A thiophene ringhas the general structure:

where the ring may carry substituents or be bonded to or fused to one ormore aryl, heteroaryl or non-aromatic carbocyclic or heterocyclic rings.

Thus, in an embodiment, the CORE comprises two or more thiophene rings.A thiophene ring of the core may be directly or indirectly linked to ormay be directly or indirectly fused to one or more thiophene ring, oneor more aryl or heteroaryl rings (other than a thiophene ring) or to oneor more non-aromatic carbocyclic or heterocyclic rings.

In embodiments, the core structure contains at least two thiophenerings, wherein

(1) the two or more thiophene rings are separated by a linker group M;

(2) the two or more thiophene rings are directly fused to each other orindirectly fused to each other through an optionally substitutedaromatic or non-aromatic carbocylic or an optionally substitutedaromatic or non-aromatic heterocyclic ring system; or

(3) each of two or more thiophene rings is fused to an aromatic ornon-aromatic carbocylic or an aromatic or non-aromatic heterocyclic ringsystem and the resulting fused rings containing a thiophene ring areeach separated by a linker group M.

The linker M can be a single bond, a double bond, or a divalent ortrivalent linker comprising an alkylene (—(CH₂)_(x), where x is 1-12,preferably 1-6, more preferably 1-4), an alkenylene (e.g., —CH═CH—), adialkenylene (e.g., —CH═CH—CH═CH—), an alkynylene (e.g., —C≡C—), adialkynylene (—C≡C—C≡C—), or an optionally substituted aromatic ornon-aromatic carbocyclic or heterocyclic ring system. In specificembodiments, the linker is linear. In specific embodiments, the linkeris branched. In specific embodiments, the linker is an alkylene, adialkenylene, an alkynylene, a dialkynylene or an optionally substitutedaromatic or non-aromatic carbocyclic or heterocyclic ring system. Inspecific embodiments the linkeris —CH═CH—, —CH═CH—CH═CH—, —C≡C—, a dialkynylene (—C≡C—C≡C—), or anoptionally-substituted aromatic or non-aromatic carbocyclic orheterocyclic ring system. In specific embodiments, M is anoptionally-substituted arylene or a heteroarylene. In specificembodiments, M is a moiety as illustrated in Scheme 2.

In specific embodiments, optional substitution of aromatic ornon-aromatic carbocyclic or heterocyclic ring systems, arylene orheteroarylene is substitution with one or more halogen, CN, alkyl oralkoxy having 1-30 carbon atoms, 1-12 carbon atoms, 3-12 carbon atoms,6-12 carbon atoms or 1-3 carbon atoms. In specific embodiments, optionalsubstitution of aromatic or non-aromatic carbocyclic or heterocyclicring systems is substitution with one or more halogens, or one or morealkyl groups

In specific embodiments, the oligomeric compounds have four or more PDIgroups therein, each of which is bonded to a core structure containingat least two thiophene rings, wherein:

-   -   (1) the two or more thiophene rings are separated by a linker        group M;    -   (2) two or more thiophene rings are directly fused to each other        or indirectly fused to each other through an optionally        substituted aromatic or non-aromatic carbocylic or an optionally        substituted aromatic or non-aromatic heterocyclic ring system;        or    -   (3) each of two or more thiophene rings is fused to an aromatic        or non-aromatic carbocylic or an aromatic or non-aromatic        heterocyclic ring system and the resulting fused rings        containing a thiophene ring are each separated by a linker group        M.

The linker M can be a single bond, a double bond, or a divalent ortrivalent linker comprising an alkylene (—(CH₂)_(x)—), an alkenylene(e.g., —CH═CH—), a dialkenylene (e.g., —CH═CH—CH═CH—), an alkynylene(e.g., —C≡C—), a dialkynylene (—C≡C—C≡C—), or an optionally substitutedaromatic or non-aromatic carbocyclic or heterocyclic ring system. Inspecific embodiments, M is an arylene or a heteroarylene.

In specific embodiments, M is a moiety as illustrated in Scheme 2(L1-L15), where:

each R₆ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms;

each R₇ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms;

each R₈ is independently selected from hydrogen, an optionallysubstituted phenyl or benzyl or an alkyl having 1-30, 1-12, 3-12, 6-12or 1-3 carbon atoms; and

R_(N) is selected from hydrogen, an alkyl group having 1-30, 1-12, 3-12,6-12 or 1-3 carbon atoms, an aryl group and an arylalkyl group. For M ofScheme 2, aryl groups include phenyl and naphthyl groups, among others,and arylalkyl groups include benzyl and phenethyl groups.

More specifically, M is:

-   -   (a) L1 or L2;    -   (b) L3 or L4;    -   (c) L5 or L6;    -   (d) L7;    -   (e) L8;    -   (f) L9 or L10;    -   (g) L, L12 or L15;    -   (h) L13; or    -   (i) L14

In specific embodiments, the CORE is a moiety C1-C40 as illustrated inScheme 3, where:

each R₄ is independently selected from H, an alkyl or alkoxy grouphaving 1-30 carbon atoms, an optionally substituted aryl or heteroarylgroup, where optional substitution is substitution with one or morehalogen, CN, alkyl or alkoxy having 1-30 carbon atoms, 1-12 carbonatoms, 3-12 carbon atoms, 6-12 carbon atoms or 1-3 carbon atoms;each R₅ is independently selected from hydrogen, halogen, CN, or alkylor alkoxy having 1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms;each R₆ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms;each R₇ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30, 1-12, 3-12, 6-12 or 1-3 carbon atoms; andR_(N) is selected from hydrogen, an alkyl group having 1-30, 1-12, 3-12,6-12 or 1-3 carbon atoms, an aryl group or an arylalkyl group.

For CORES of Scheme 3, aryl groups include phenyl and naphthyl groups,among others, and arylalkyl groups include benzyl and phenethyl groups.

In specific embodiments of CORES of Scheme 3, each R₆ is hydrogen. Inspecific embodiments of CORES of Scheme 3, each R₆ is an alkyl grouphaving 1-6 carbon atoms. In specific embodiments of CORES of Scheme 3,each R₇ is hydrogen, or a halogen and more specifically, each R₇ ishydrogen or fluorine and in a further embodiment, one R₇ is hydrogen andthe other R₇ is fluorine. In specific embodiments of the CORES of Scheme3, each R₈ is hydrogen. In specific embodiments, each R₈ is an alkylgroup having 1-6 carbon atoms. In specific embodiments of CORES ofScheme 3, each R₇ is independently hydrogen or halogen or yet morespecifically, each R₇ is independently hydrogen or fluorine. In specificembodiments, each R_(N) is hydrogen or an alkyl group having 1-12 carbonatoms or an alkyl group having 1-3 carbon atoms.

More specifically, the CORE is:

-   -   a) the moiety C1, C2, C6 or C7;    -   b) the moiety C3, C4 or C5;    -   c) the moiety C8, C9 or C35;    -   d) the moiety C10 or C11;    -   e) the moiety C12;    -   f) the moiety C13;    -   g) the moiety C14, C15 or C16;    -   h) the moiety C17 or C18;    -   i) the moiety C19a (Y is C), C19b (Y is P), C19c (Y is N), C19d        (Y is S), C19e (Y is Si), or C19f(Y is Ge);    -   j) the moiety C19a, C19c or C19d);    -   k) the moiety C20a, C20b or C20c;    -   l) the moiety C21, C23 or C24;    -   m) the moiety C22 or C25;    -   n) the moiety C26 or C27;    -   o) the moiety C28 or C29;    -   p) the moiety C30, C31, C32, or C33;    -   q) the moiety C34 or C36;    -   r) the moiety C37;    -   s) the moiety C38;    -   t) the moiety C39; or    -   u) the moiety C40.

In a specific embodiment, the core precursor has structure:

and the oligomer is:

where -M- is a single bond, an alkylene (—(CH₂)_(x)—), an alkenylene(e.g., —CH═CH—), a dialkenylene (e.g., —CH═CH—CH═CH—), an alkynylene(e.g., —C≡C—), a dialkynylene (—C≡C—C≡C—), or an optionally substitutedaromatic or non-aromatic carbocyclic or heterocyclic ring system. Inspecific embodiments, M is an arylene or a heteroarylene. In specificembodiments, M is a moiety as illustrated in Scheme 2. In an embodiment,M itself does not contain a thiophene ring with one or more active C—Hgroups. M may however contain a thiophene ring with no active C—H bonds.

In a specific embodiment, the core precursor has structure:

and the oligomer is:

where -M- is a single bond, an alkylene (—(CH₂)_(x)—), an alkenylene(e.g., —CH═CH—), a dialkenylene (e.g., —CH═CH—CH═CH—), an alkynylene(e.g., —C≡C—), a dialkynylene (—C≡C—C≡C—), or an optionally substitutedaromatic or non-aromatic carbocyclic or heterocyclic ring system. Inspecific embodiments, M is an arylene or a heteroarylene. In specificembodiments, M is a moiety as illustrated in Scheme 2. In an embodiment,M itself does not contain a thiophene ring with one or more active C—Hgroups. M may however contain a thiophene ring with no active C—H bonds.

In a specific embodiment, the core precursor has structure:

and the oligomer has structure:

where R₄ is as defined above. In specific embodiments, each R₄ is alkyl.In specific embodiments, each R₄ is alkoxy. In specific embodiments,each R₄ is optionally substituted aryl. In specific embodiments, each R₄is optionally substituted phenyl. Optional substitution is substitutionof a phenyl with 1-4 non-hydrogen substituents selected from halogen,alkyl or alkoxy having 1-12 carbon atoms, or CN.

In a specific embodiment, the core precursor has structure:

and the oligomer has structure:

where each R₅ is as defined above and in specific embodiments each R₅ isan alkyl group. In an embodiment all R₅ are the same group. In anembodiment, each R₅ is a straight-chain alkyl of 3-12 or 3-8 carbonatoms. In a specific embodiment each R₅ is —C₆H₁₃. In other embodiments,each R₅ is a branched alkyl group. In specific embodiments, each R₅ isselected from branched alkyl groups of formula —C(Ra)(Rb), where Ra andRb are, independently, alkyl groups having 2-10 carbon atoms. Inspecific embodiments, Ra and Rb are the same alkyl group. In specificembodiments, Ra and Rb are different alkyl groups. In specificembodiments, Ra and Rb are straight-chain alkyl groups. In specificembodiments, each R₅ is independently a 1-ethylpropyl, 1-propylbutyl,1-butylpentyl, 1-pentylhexyl, 1-hexylheptyl, 1-heptyloctyl,1-octylnonyl, 1-nonyldecyl, or 2-ethylhexyl.

In an embodiment, the oligomer of the invention has CORE of structure:

where R₆ is independently selected from hydrogen, halogen, CN, anoptionally substituted phenyl or benzyl or an alkyl or alkoxy having1-30 carbon atoms. In more specific embodiments, R₆ is hydrogen or analkyl group having 1-12 carbon atoms. In more specific embodiments, R₆is hydrogen or an alkyl group having 1-6 carbon atoms. In more specificembodiments. In more specific embodiments of compounds of core LV, inPDI, Y is NR3. In more specific embodiments of compounds of core LV, inPDI, Y is S or Se. In more specific embodiments of compounds ofcompounds of core LV, in PDI, R₁ and R₂ are alkyl groups having 6-12carbon atoms.

In specific embodiments, tetramers of the disclosure include:

In specific embodiments of IVA-IVG, in PDI groups, Y is N—R₃.

In specific embodiments, hexamers of the disclosure include:

In specific embodiments of VIA or VIB, in PDI groups, Y is N—R₃.

In specific embodiments, hexamers of the disclosure include:

In specific embodiments of VIIIA in PDI groups, Y is N—R₃.

In specific embodiments, the cores of tetramers herein include:

In specific embodiments, the cores of tetramers herein include:

In specific embodiments, the cores of tetramers herein include:

In specific embodiments, the cores of tetramers herein include:

where n is 0, 1 or 2, R′ is H or an alkyl having 1-15 carbon atoms.

In specific embodiments, the cores of tetramers herein are other than 3,3′-bithiophene.

In specific embodiments, the cores of tetramers herein are other than:

In specific embodiments, the cores of tetramers herein are other than:

In specific embodiments, the cores of tetramers herein are other than:

where n is 0, 1 or 2, R′ is H or an alkyl having 1-15 carbon atoms.

In specific embodiments, the cores of tetramers herein are other than

where:z is 0 or 1 and M1 is an arylene, a heteroarylene, or an organic dyemolecule.

In an aspect, the invention relates to a method of making the oligomericPDI compound herein which comprises reacting a core precursor carrying 4or more C—H bonds that are active for direct arylation or directheteroarylation with 2 or more equivalents with respect to the amount ofcore precursor of the PDI precursor of formula XI, wherein X is a goodleaving group, such as Br.

Scheme 1A illustrates a generic reaction of the disclosure in which N(which is 4 or more) PDI units are bonded to a multivalent core having N(4 or more)C—H bonds which are active for DHA coupling with a Pdcatalyst.

Scheme 1B illustrates a more specific reaction of the in which 4 PDIunits are bonded to a tetrameric core (containing 4 active C—H bondswhich are indicated by “*”) to form a tetramer. The reaction isconducted in an appropriate solvent above room temperature and isillustrated to employ at least the stoichiometric amount of the PDIprecursor to form the tetramer. Specific reagents, solvents and reactionconditions are illustrated herein and in the Examples.

More specifically, if the oligomer is a tetramer, it is preferred toemploy 4 or more equivalents of the PDI precursor. More specifically, ifthe oligomer is a hexamer, it is preferred to employ 6 or moreequivalents of the PDI precursor. More specifically, if the oligomer isan octamer, it is preferred to employ 8 or more equivalents of the PDIprecursor. More specifically, if the oligomer is a decamer, it ispreferred to employ 10 or more equivalents of the PDI precursor.Generally, it is preferred to employ from 1-10% in excess of thestoichiometric amount of the PDI precursor needed to form the desiredoligomeric PDI compound.

The reaction is generally conducted in a solvent in which the PDIprecursor and the core precursor are at least partially soluble. Usefulsolvents include dimethylacetamide (DMA), dimethylformamide (DMF),tolulene, xylene(s), tetrahydrofuran. One of ordinary skill in the artcan select an appropriate solvent for a given set of reactants in viewof what isexemplified herein and in view of what is known in the art.

The reaction is typically conducted at temperatures above ambient roomtemperature. More specifically the reaction is conducted at atemperature greater than 50° C. and more preferably at a temperaturegreater than 70° C. and yet more preferably at a temperature greaterthan 100° C. The upper temperature limit of the reaction at ambient roompressure is generally about the boiling point of the selected solventand the reaction is conducted under reflux. In a specific embodiment,the reaction is carried out in a sealed vessel at about ambient roompressure at temperatures greater than 50 OC and more preferably at atemperature greater than 70 OC and yet more preferably at a temperaturegreater than 100° C. In a specific embodiment, the reaction is carriedout in a sealed vessel at a temperature ranging from 70° C. to 130° C.,or more preferably at a temperature ranging from 80° C. to 130° C., ormore preferably at a temperature ranging from 100° C. to 130° C. Asillustrated in the examples herein, increasing reaction temperature ofthe sealed reaction vessel can result in yield improvements. One ofordinary skill in the art can select appropriate reaction temperaturefor a given solvent and a given set of reactants in view of what isexemplified herein and in view of what is known in the art.

The reaction is conducted in the presence of a DHA catalyst, such as apalladium catalyst. Exemplary Pd catalysts are Pd(PPh₃)₄ or Pd(OAc)₂. Ina specific embodiment, the Pd catalyst is a catalyst with adiphenylphosphine ligand and that catalyst may be attached to a silicasupport. In an embodiment, the catalyst is a heterogeneous Pd catalystof formula:

such as the commercially available heterogeneous Pd catalyst SiliaCat®DPP-Pd (see web site silicycle.com). One of ordinary skill in the artcan select an appropriate catalyst for the desired DHA reaction and theselected reactants, solvent and reaction conditions in view of what isexemplified herein and in view of what is known in the art.

It is preferred to prepare a given oligomeric compound substantiallyfree of other oligomers. For example a tetramer is preferably preparedsubstantially free of corresponding dimers, trimers and higheroligomers. Substantially free of other oligomers means that the desiredoligomer contains less than 1% by weight of other oligomers. Preferablythe desired oligomer is prepared with less than 0.5% by weight of otheroligomers. The oligomer prepared is generally controlled by controllingthe stoichiometry of the added reactants and the reaction conditions, asillustrated in the examples herein. Undesired oligomers, if present, canbe removed by selected washing with solvent as illustrated in theexamples herein. However, alternatively or in combination, crude productor washed product can be purified by silica gel column chromatographyemploying an appropriate solvent gradient, e.g., a hexane todichoromethane gradient. It will be appreciated that purification steps,such as elution time, can vary dependent upon the given oligomer, andreactants employed.

One of ordinary skill in the art will recognize that starting materialsand reagents other than those specifically disclosed in the Examples canbe employed in the reactions herein without resort to undueexperimentation. One of ordinary skill in the art knows how to selectappropriate starting materials for alkylation and to if necessary adjustthe solvent employed.

In certain compounds of this invention, in the core of the oligomer, adivalent, trivalent or tetravalent moiety (linker M) links two, three orfour thiophene or other thiophene-containing moieties. Divalent moietiesuseful in compounds of the invention include, among others:

a single bond,

alkenylene groups containing 1 double bond, such as:

containing one double bond; oror those containing 2 double bonds (also designated dialkenylenegroups), such as

alkynylene groups, containing 1 triple bond, such as:

or those containing 2 triple bonds (also designated dialkynylenegroups), such as:

A divalent arylene moiety is derived from an aromatic hydrocarbonformally by removal of two hydrogens. A trivalent arylene moiety isderived from an aromatic hydrocarbon formally by removal of threehydrogens. A tetravalent arylene moiety is derived from an aromatichydrocarbon formally by removal of four hydrogens arylene groups hereininclude those derived from an aromatic hydrocarbon have one or morearomatic hydrocarbon rings which include those with fused rings. Morespecifically, the arylene group can include 1, 2, 3 or 4 aromatic rings.In specific embodiments, arylene groups are optionally substituted withone or more alkyl groups, halogens or CN groups.

Divalent moieties include arylene groups having available two sites ofattachment:

Di-, tri- or tetravalent aromatic linkers include those where thearomatic rings are bonded to each other by one or more single bonds (asin biphenylenes above) and are also exemplified by:

Each of the exemplified linkers above is optionally substituted with oneor more alkyl groups, halogens, nitro groups or CN groups.

Di-, tri- or tetravalent linkers include those that are derived fromheteroaromatic compounds. Heteroaromatic compounds include those havingone or more aromatic rings that have at least one heteroatom, e.g., N, Oor S. In specific embodiments, heteroaromatic compounds have at leastone 5- or 6-member heteroaromatic ring. In a specific embodiment, theheteroaromtic linker can be an oligomer having 1-8 repeats of theheteroaromatic ring(s).

Divalent heteroaromtic linkers include:

here V is O, S or Se and t is 1, 2, 3, 4, 5, 6, 7 or 8.

Additional exemplary M groups are illustrated in Scheme 2.

It will be appreciated that trivalent and tetravalent moieties or groupsillustrated in Scheme 3 can be converted into divalent groups bysubstitution of one or two hydrogens, alkyl groups (e.g., a C₁₋₁₂, C₁₋₆,C₆₋₁₂, C₁₋₃, C₃₋₉ or C₃₋₆ alkyl group) or another non-hydrogensubstituent (e.g., a nitro group, a cyano group or a halogen) at one(for trivalent moieties) or two (for tetravalent moieties) of thepossible bonding sites on the moiety. Similarly a tetravalent moiety canbe converted to a trivalent moiety.

The term alkyl refers to a monovalent group formally derived from asaturated hydrocarbon group by removal of a hydrogen. An alkyl group hasthe general formula C_(n)H_(2n+1). Alkyl groups can be straight-chain(linear) or branched. Alkyl groups herein can have 1-30 carbon atoms andmore preferably 1-20 carbon atoms. Branched alkyl groups herein can have3-30 carbon atoms and more preferably 3-20 carbon atoms. Straight-chainalkyl groups include those having 1-3 carbon atoms, 1-6 carbon atoms,4-8 carbon atoms, 6-12 carbon atoms, and 6-20 carbon atoms, among othergroups of carbon atom range. Straight-chain alkyl groups include methyl,ethyl, propyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl individuallyor in any combination. Branched alkyl groups include isopropyl,iso-butyl, sec-butyl, 1-ethylpropyl, 1-propylbutyl, 1-butylpentyl,1-pentylhexyl, lhexylheptyl, 1-heptyloctyl, 1-octylnonyl, 1-nonyldecyl,2-ethylhexyl individually or in any combination. Branching may occuranywhere along the alkyl chain from the site of attachment of the alkylgroup. For example, a branch may occur at the first carbon (as inal-ethylpropyl group). The branching can occur for example at the secondcarbon along the chain (e.g., 2-ethylhexyl). There may be multiplebranches along the chain (e.g., 1-ethyl-5-methylhexyl). In specificembodiments, a branched alkyl chain has one branching point which is atthe first, second or third carbon from the site of attachment.

Cycloalkyl is a subset of alkyl groups having a carbon ring of 3 or moreatoms, typically 3-12 atoms and more typically 3-10 atoms. In specificembodiments, cycloalkyl groups have 3, 4, 5, 6, 7 or 8 member carbonrings. Herein a cycloalkyl can replace an alkyl group. Specificcycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl and cyclodecyl groups.Cycloalkyl groups are optionally substituted.

An alkoxy group is an alkyl group, as broadly discussed above, linked tooxygen (R_(alkyl)—O—).

A divalent alkyl group (e.g., for a straight-chain group —(CH₂)_(p)—,where p is 1-12) is called an alkylene group herein. Such a group isattached between two other moieties by formation of a bond to twocarbons in the group. The alkylene group is an exemplary linker herein.Alkylene groups may be straight-chain or branched and are optionallysubstituted with one or more non-hydrogen substituents. Alkylene groupsinclude those having 2-12, 2-8, 2-6 or 2-4 carbon atoms. Linker groups(L1) herein include alkylene groups, particularly straight chain,unsubstituted alkylene groups, —(CH₂)n-, where n is 1-12, n is 1-10, nis 1-9, n is 1-8, n is 1-7, n is 1-6, n is 1-5, n is 1-4, n is 1-3, n is2-10, n is 2-9, n is 2-8, n is 2-7, n is 2-6, n is 2-5 or n is 2-4. Arylgroups include groups having one or more 5- or 6-member aromatic rings.Aryl groups can contain one, two or three, 6-member aromatic rings. Arylgroups can contain two or more fused aromatic rings. Aryl groups cancontain two or three fused aromatic rings. Aryl groups are optionallysubstituted with one or more non-hydrogen substituents. Substituted arylgroups include among others those which are substituted with alkyl oralkenyl groups, which groups in turn can be optionally substituted.Specific aryl groups include phenyl groups, biphenyl groups, andnaphthyl groups, all of which are unsubstituted or optionallysubstituted as described herein. Substituted aryl groups include fullyhalogenated or semihalogenated aryl groups, such as aryl groups havingone or more hydrogens replaced with one or more fluorine atoms, chlorineatoms, bromine atoms and/or iodine atoms. Substituted aryl groupsinclude fully fluorinated (perfluorinated) or partially fluorinated arylgroups, such as aryl groups having one or more hydrogens replaced withone or more fluorine atoms.

Arylalkyl groups are those in which an alkyl group is substituted withan aryl group. Arylalkyl groups include benzyl and phenethyl groupsamong others. Most generally alkyl groups are straight-chain or branchedas described herein. In specific embodiments, the alkyl groups ofarylalkyl groups have 1-6 carbon atoms and more preferably 1-3 carbonatoms. Arylalkyl groups can contain any aryl group as described herein.Arylalkyl groups are optionally substituted as described herein.Substituted arylalkyl groups include those in which the aryl group issubstituted with 1-5 non-hydrogen substituents and particularly thosesubstituted with 1, 2 or 3 non-hydrogen substituents. Usefulsubstituents include among others, methyl, methoxy, hydroxy, halogen,and nitro. Particularly useful substituents are one or more halogens.Specific substituents include F. Cl, and nitro.

A divalent arylene (AR) moiety is derived from an aromatic hydrocarbonformally by removal of two hydrogens. Arylene groups herein includethose derived from an aromatic hydrocarbon have one or more aromatichydrocarbon rings which include those with fused rings. Morespecifically, the arylene group can include 1, 2, 3 or 4 aromatic rings.In specific embodiments, arylene groups are optionally substituted withone or more alkyl groups, halogens or CN groups. Arylene groups includeamong others phenylene, biphenylene, and naphthylene.

A heterocyclic (or herterocycyl) group is a group having one or moresaturated or unsaturated carbon rings and which contains one to threeheteroatoms (e.g., N, O or S) per ring. These groups optionally containone, two or three double bonds. To satisfy valence requirement, a ringatom may be substituted as described herein. One or more carbons in theheterocyclic ring can be —CO— groups. Heterocyclic groups include thosehaving 3-12 carbon atoms, and 1-6, heteroatoms, wherein 1 or 2 carbonatoms are replaced with a —CO— group. Heterocyclic groups include thosehaving 3-12 or 3-10 ring atoms of which up to three can be heteroatomsother than carbon. Heterocyclic groups can contain one or more ringseach of which is saturated or unsaturated. Heterocyclic groups includebicyclic and tricyclic groups. Preferred heterocyclic groups have 5- or6-member rings. Heterocyclic groups are optionally substituted asdescribed herein. Specifically, heterocyclic groups may be substitutedwith one or more alkyl groups. Heterocyclic groups include those having5- and 6-member rings with one or two nitrogens and one or two doublebonds. Heterocyclic groups include those having 5- and 6-member ringswith an oxygen or a sulfur and one or two double bonds. Heterocyclicgroup include those having 5- or 6-member rings and two differentheteroatom, e.g., N and O, O and S or N and S. Specific heterocyclicgroups include among others, pyrrolidinyl, piperidyl, piperazinyl,pyrrolyl, pyrrolinyl, furyl, thienyl, morpholinyl, oxazolyl, oxazolinyl,oxazolidinyl, indolyl, triazoly, and triazinyl groups.

Heteroaryl groups include groups having one or more aromatic rings inwhich at least one ring contains a heteroatom (a non-carbon ring atom).Heteroaryl groups include those having one or two heteroaromatic ringscarrying 1, 2 or 3 heteroatoms and optionally have one 6-member aromaticring. Heteroaryl groups can contain 5-20, 5-12 or 5-10 ring atoms. Ringsof the group may be fused. Heteroaryl groups include those having onearomatic ring contains a heteroatom and one aromatic ring containingcarbon ring atoms. Heteroaryl groups include those having one or more 5-or 6-member aromatic heteroaromatic rings and one or more 6-membercarbon aromatic rings. Heteroaromatic rings can include one or more N,O, or S atoms in the ring. Heteroaromatic rings can include those withone, two or three N, those with one or two O, and those with one or twoS, or combinations of one or two or three N, O or S. Specific heteroarylgroups include furyl, pyrrolyl, pyridinyl, pyrazinyl, pyrimidinyl,quinolinyl, purinyl, thiophenyl, or indolyl groups.

Heteroatoms include O, N, S, P or B. More specifically heteroatoms areN, O or S. In specific embodiments, one or more heteroatoms aresubstituted for carbons in aromatic or carbocyclic rings. To satisfyvalence any heteroatoms in such aromatic or carbocyclic rings may bebonded to H or a substituent group, e.g., an alkyl group or othersubstituent.

The term carbocyclic refers generally to a hydrocarbon having one ormore carbon rings, wherein the rings are not aromatic rings. Aryl andheteroaryl groups include those with 5 or 6-member rings. Carbocyclicrings include those with 3-12 member carbon rings. Carbocyclic rings caninclude bicyclic and tricyclic rings.

As to any of the above groups which contain one or more substituents, itis understood, that such groups do not contain any substitution orsubstitution patterns which are sterically impractical and/orsynthetically non-feasible. In addition, the compounds of this inventioninclude all stereochemical isomers arising from the substitution ofthese compounds.

With respect to the various compounds of the disclosure, the atomstherein may have various isotopic forms (e.g., isotopes of hydrogeninclude deuterium and tritium). All isotopic variants of compounds ofthe disclosure are included within the disclosure and particularlyinclude deuterium and 13C isotopic variants. It will be appreciated thatsuch isotopic variants may be useful for carrying out various chemicaland biological analyses, investigations of reaction mechanisms and thelike. Methods for making isotopic variants are known in the art.

Compounds of the disclosure can be prepared by one of ordinary skill inthe art in view of the descriptions provided herein and what is known inthe art from commercially or otherwise readily available startingmaterials and reagents. As described herein in the Examples, knownsynthetic methods can be readily adapted for synthesis of the compoundsof the formulas herein.

Compounds of the disclosure may contain chemical groups (acidic or basicgroups) that can be in the form of salts. Exemplary acid addition saltsinclude acetates (such as those formed with acetic acid or trihaloaceticacid, for example, trifluoroacetic acid), adipates, alginates,ascorbates, aspartates, benzoates, benzenesulfonates, bisulfates,borates, butyrates, citrates, camphorates, camphorsulfonates,cyclopentanepropionates, digluconates, dodecylsulfates,ethanesulfonates, fumarates, glucoheptanoates, glycerophosphates,hemisulfates, heptanoates, hexanoates, hydrochlorides (formed withhydrochloric acid), hydrobromides (formed with hydrogen bromide),hydroiodides, 2-hydroxyethanesulfonates, lactates, maleates (formed withmaleic acid), methanesulfonates (formed with methanesulfonic acid),2-naphthalenesulfonates, nicotinates, nitrates, oxalates, pectinates,persulfates, 3-phenylpropionates, phosphates, picrates, pivalates,propionates, salicylates, succinates, sulfates (such as those formedwith sulfuric acid), sulfonates (such as those mentioned herein),tartrates, thiocyanates, toluenesulfonates such as tosylates,undecanoates, and the like.

Exemplary basic salts include ammonium salts, alkali metal salts such assodium, lithium, and potassium salts, alkaline earth metal salts such ascalcium and magnesium salts, salts with organic bases (e.g., organicamines) such as benzathines, dicyclohexylamines, hydrabamines [formedwith N,N-bis(dehydro-abietyl)ethylenediamine], N-methyl-D-glucamines,N-methyl-D-glucamides, t-butyl amines, and salts with amino acids suchas arginine, lysine and the like. Basic nitrogen-containing groups maybe quaternized with agents such as lower alkyl halides (e.g., methyl,ethyl, propyl, and butyl chlorides, bromides and iodides), dialkylsulfates (e.g., dimethyl, diethyl, dibutyl, and diamyl sulfates), longchain halides (e.g., decyl, lauryl, myristyl and stearyl chlorides,bromides and iodides), aralkyl halides (e.g., benzyl and phenethylbromides), and others.

Compounds of the invention may include salts and solvates of compoundsof formulas herein. Solvates include solvates of salts. Solvatesinclude, among others, hydrates.

Compounds of the present disclosure, and salts thereof, may exist intheir tautomeric form, in which hydrogen atoms are transposed to otherparts of the molecules and the chemical bonds between the atoms of themolecules are consequently rearranged. It is understood that alltautomeric forms, insofar as they may exist, are included within thedisclosure. Additionally, compounds may have trans and cis isomers andmay contain one or more chiral centers, therefore exist in enantiomericand diastereomeric forms. The invention includes all such isomers, aswell as mixtures of cis and trans isomers, mixtures of diastereomers andracemic mixtures of enantiomers (optical isomers). When no specificmention is made of the configuration (cis, trans or R or S) of acompound (or of an asymmetric carbon), then any one of the isomers or amixture of more than one isomer is intended.

The processes for preparation can use racemates, enantiomers, ordiastereomers as starting materials. When enantiomeric or diastereomericproducts are prepared, they can be separated by conventional methods,for example, by chromatographic or fractional crystallization. Theinventive compounds may be in the free or hydrate form. The termenantiomerically pure refers to a sample containing molecules of a givenstructure whose molecules have the same chirality sense (i.e., are thesame optical isomer) within the limits of detection. The termsubstantially enantiomerically pure refers to a sample containingmolecules of a given structure, wherein equal to or less than 1% of themolecules of the sample have a different chirality sense. Compounds ofthe invention include those which are enatiomerically pure and thosethat are substantially enatiomerically pure.

In embodiments, the disclosure provides an electronic device employingan electron acceptor wherein the electron acceptor is one or morecompounds of formulas herein.

In embodiments, the disclosure provides an organic solar cell, whichcomprises one or more compounds of any one of the formulas herein whichis an electron acceptor.

In embodiments, the disclosure provides an organic thin film transistor,which comprises one or more compounds of any one of the formulas hereinwhich is an electron acceptor.

In embodiments, the disclosure provides a redox flow battery, whichcomprises one or more compounds of any one of the formulas herein whichis an electron acceptor.

Those of ordinary skill in the art will appreciate that methods for thepreparation of organic solar cells, organic thin film transistors andredox flow batteries are known in the art and can be applied employingmaterials of the formulas herein. In view of what is known in the artand what is described herein one of ordinary skill in the art can employmaterials described and characterized herein in such devices withoutresort to undue experimentation.

Additional details of the synthesis, characterization and application ofoligomeric PDI materials are provided in references cited herein and anysupporting information of each of these references, which is freelyavailable on-line for the publisher. For example, references^(47,48)(Payne et al., 2018; Welsh et al., 2019, respectively) provideadditional examples of synthesis of oligomers as described herein andare each incorporated by reference herein in its entirety for syntheticmethods, examples methods and example starting materials and oligomers.

Additional details of processing of materials, such as oliogmeric PDImaterials of the invention, and the preparation of devices, such asorganic solar cells are provided in certain references cited herein andany supporting information of each of these references which is freelyavailable on-line for the publisher. Each of the references cited hereinand any corresponding supporting information is incorporated byreference herein in its entirety for such additional details includingsynthetic methods for starting materials, purification methods,characterization of compounds, processing of oligomeric PDT materials,components of devices employing these materials and methods for suchcharacterization, construction and testing of organic solar cell, aswell as structure and components of organic solar cells.

All references throughout this application, for example patent documentsincluding issued or granted patents or equivalents; patent applicationpublications; and non-patent literature documents or other sourcematerial; are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference.

All patents and publications mentioned in the specification areindicative of the levels of skill of those skilled in the art to whichthe invention pertains. References cited herein are incorporated byreference herein in their entirety to indicate the state of the art, insome cases as of their filing date, and it is intended that thisinformation can be employed herein, if needed, to exclude (for example,to disclaim) specific embodiments that are in the prior art. Forexample, when a compound is claimed, it should be understood thatcompounds known in the prior art, including certain compounds disclosedin the references disclosed herein (particularly in referenced patentdocuments), are not intended to be included in the claim.

When a group of substituents is disclosed herein, it is understood thatall individual members of those groups and all subgroups, including anyisomers and enantiomers of the group members, and classes of compoundsthat can be formed using the substituents are disclosed separately. Whena compound is claimed, it should be understood that compounds known inthe art including the compounds disclosed in the references disclosedherein are not intended to be included. When a Markush group or othergrouping is used herein, all individual members of the group and allcombinations and subcombinations possible of the group are intended tobe individually included in the disclosure.

Every formulation or combination of components described or exemplifiedcan be used to practice the invention, unless otherwise stated. Specificnames of compounds are intended to be exemplary, as it is known that oneof ordinary skill in the art can name the same compounds differently.When a compound is described herein such that a particular isomer orenantiomer of the compound is not specified, for example, in a formulaor in a chemical name, that description is intended to include eachisomers and enantiomer of the compound described individual or in anycombination.

One of ordinary skill in the art will appreciate that methods, deviceelements, starting materials, and synthetic methods other than thosespecifically exemplified can be employed in the practice of theinvention without resort to undue experimentation. All art-knownfunctional equivalents, of any such methods, device elements, startingmaterials, and synthetic methods are intended to be included in thisinvention. Whenever a range is given in the specification, for example,a temperature range, a time range, or a composition range, allintermediate ranges and subranges, as well as all individual valuesincluded in the ranges given are intended to be included in thedisclosure.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of” excludes any element, step, or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof” does not exclude materials or steps that do not materially affectthe basic and novel characteristics of the claim. For compositions asclaimed herein, the term consisting essentially of excludes anycomponent that detrimentally and materially affects the properties ofthat composition for use in an application recited herein, such as useof the composition as an electron acceptor particularly in an electronicdevice or more specifically in a thin film transistor, a redox flowbattery

Any recitation herein of the term “comprising”, particularly in adescription of components of a composition or in a description ofelements of a device, is understood to encompass those compositions andmethods consisting essentially of and consisting of the recitedcomponents or elements. The invention illustratively described hereinsuitably may be practiced in the absence of any element or elements,limitation or limitations which is not specifically disclosed herein.

Without wishing to be bound by any particular theory, there can bediscussion herein of beliefs or understandings of underlying principlesrelating to the invention. It is recognized that regardless of theultimate correctness of any mechanistic explanation or hypothesis, anembodiment of the invention can nonetheless be operative and useful.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by preferredembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of this invention.

THE EXAMPLES Example 1

IDT flanked with N-annulated PDI (IDT-NPD12) as shown in Scheme 4 was aninitial target of continuing work in view of previous success ofN-annulated perylene diimide materials³³ as non-fullerene acceptors andPDI-IDT compounds showing good OPV performance³⁴⁻³⁶ Using optimized DHAconditions, IDT was reacted with 2.0 equivalents of the activated PDIstarting material NPDI-Br (FIG. 1A). Unexpectedly, the reactionproceeded almost exclusively, albeit in relatively low yield, to thetetra-substituted product, IDT-NPDI4, instead of the expectedbis-substituted product.

To probe this unexpected reactivity, the same reaction was performedwith 4.2 equivalents of NPDI-Br which was found to result in a mixtureof both starting materials, mono-, bis-, tris- and tetra-substitutedproducts, suggesting a stepwise reaction (FIG. 1B). The individualproducts proved difficult to separate by silica-gel columnchromatography, but the fractions isolated were characterized by massspectroscopy and found to be mono-, bis-, tris-, and tetra-substitutedproducts. The ¹H NMR spectra were convoluted, especially for thebis-substituted product suggesting product mixtures of varioussubstitutions i.e. 2′2, 2′3, 3′3. Typically, these alternatesubstitutions are unwanted and have been seen as a major drawback of DHAreactions which has resulted in studies addressing this unselective C—Hactivation and how it can be mitigated. This is particularly seen as aproblem in direct heteroarylation polymerization (DHAP) reactions whereonce formed, such ‘defect’ structures are covalently incorporated intothe polymer backbone and cannot be removed.⁹⁻¹¹ However, it was foundthat this direct reactivity could be exploited to access new materials,specifically those with tetra and higher PDI-substituted thiophene-basedcores. It was determined that increasing the reaction temperature couldbe employed to drive the reaction to further completion resulting in thetetramer as the main product with only a small amount oftris-substitution. It was also found that the tris-substituted productcould be removed by an ethyl acetate wash and the tetrameric product,IDT-NPDI4, was isolated as a fine dark red crystalline powder in 62%yield (FIG. 1C). The IDT-NPDI4 tetramer structure as shown, wasconfirmed by NMR spectroscopy MALDI-TOF mass spectrometry and elementalanalysis.

For example, the aromatic region of the ¹H NMR spectrum of IDT-NPD14 isdepicted in FIG. 1. The downfield shifted peaks between 8.4-9.2 ppm areattributed to NPDI (10 NPDI protons for the half molecule). The peakscorresponding to the electron rich IDT core

remain further upfield with the singlet at 7.37 ppm corresponding to thepara protons on the central phenyl ring of the IDT core. The opticalproperties of IDT-NPDI4 were evaluated using UV-Vis spectroscopy (FIG.2A, Table 1), photoluminescence spectroscopy (FIG. 2B, Table 1). Asexpected, with four PDI units, the UV-Vis profile is dominated by NPDIwith a high molar absorptivity surpassing 200,000 M−1cm-1, which isapproximately four times that observed for monomeric PDI species. Thehigher energy absorption from 350-440 nm is attributed to the IDT core.The lack of any significant lower energy absorption bands indicates thatthere is minimal electron delocalization between the IDT and NPDI unitswhich can be expected due to the likelihood of large dihedral anglesbetween the building blocks as a result of the inherent steric strains.

Large dihedral angles of 180° between the NPDI units and IDT core areobserved for the theoretical optimized structure calculated by densityfunctional theory (DFT) at the B3LYP-6-31G(d,p) level of theory. As canbe seen in FIGS. 3A and 3B, the NPDI backbones in the calculatedstructure are orthogonal to that of IDT giving the molecule abutterfly-type shape.

Minimal change in optical absorption is observed upon transitioning fromsolution to film suggesting no significant change in molecularorganization from solution to solid state. Thin film UV-Vis spectra ofthe individual components (IDT and NPDI) of IDT-NPDI4 can be viewed inFIG. 4B and assist in the assignment of the optical transitions. Thephotoluminescence spectra show relatively large stokes shifts forIDT-PDI4 in both solution (0.67 eV) and solid state (0.64 eV).Typically, PDI compounds exhibit small stoke shifts so it is postulatedthat this large red-shifted emission observed may be the result of anintramolecular charge transfer state. Structures of IDT, NPDI andIDT-NPDI4 are shown in FIG. 4A.

The electronic properties were investigated using cyclic voltammetry(FIGS. 5A and 5B, Table 2). IDT-NPDI4 shows stable ambipolar redoxbehaviour with two reversible oxidations, the first being attributed toIDT (E1/2=0.61 V) and the second NPDI (E1/2=1.00 V), and two reversiblereductions attributed to NPDI (E1/2=−1.32 V, −1.59 V). The assignmentsof the oxidation and reduction waves are based on the overlaid cyclicvoltammograms of IDT-PDI4 with its individual components, IDT and NPDI(FIG. 5B). The ionization potentials (IP) and electron affinities (EA)were estimated by correlating the onsets of oxidation and reduction,respectively, to the normal hydrogen electrode (NHE), assuming the IP ofFc/Fc+ to be 4.80 eV. The IP, dominated by the IDT core, was found to be5.3 eV and the EA, dictated by the NPDI units, was calculated at 3.6 eV.

OSC devices were fabricated using the standard donor polymer PTB7-Thwith the exemplary tetramer IDT-NPDI4 as the NFA. An inverted bulkheterojunction (BHJ) architecture was utilized with active layerprocessing from chlorobenzene with the solvent additivechloronaphthalene (CN), a common processing method found to improvedevice performance of PDI OSCs. OSC characterization and device metricsare detailed in FIGS. 6A-D and Table 3. The PTB7-Th:IDT-NPDI4-based OSCsshowed a good photovoltaic response with devices reaching powerconversion efficiencies (PCEs) of 3.4% using 5% v/v CN processingadditive. As seen in FIG. 6A, the OCS produced high voltages (VOC) above1V, but ultimately had modest currents (JSC) from 8-10 mA cm-2 and poorfill factors (FF). Photocurrent generation occurred from 300-800 nm witha maximum from 500-550 nm, which is where IDT-NPDI4 absorbs indicatingits significant contribution to photocurrent generation (FIG. 6B).Investigation of the active layer morphology of the best OSC via atomicforce microscopy (AFM, FIGS. 6C and 6D) revealed a very smooth film. Theelectron and hole mobility of the active layer was determined via thespace charge limited current (SCLC) method and found to be 4.00×10−6cm2V−1s−1 and 2.74×10−4 cm2V−1s−1, respectively (FIGS. 7A and B,respectively). The unbalanced charge transport of the active layer isthe primary cause of the lower FF and JSC in this case. Indeed, theshunt resistance is low indicating that free charge carriers are beinggenerated, but not being collected fast enough. These results are quiteencouraging as the JSC and FF can be improved through further activelayer processing optimization.

TABLE 1 Tabulated optical absorption data λ_(max) abs λ_(onset) abs Egε(λ_(max)) λ_(max) Stokes (nm) (nm) (eV) (M⁻¹cm⁻¹) em (nm) Shift (eV)Solution 533 568 2.2 209,803 748 0.67 Film 533 574 2.2 732 0.64

TABLE 2 Tabulated electrochemical data Oxidation Reduction PotentialsOx_(onset) IP Potentials Red_(onset) EA Eg (V) (V) (eV) (V) (V) (eV)(eV) 0.61, 1.00 0.50 5.3 −1.32, −1.20 3.6 1.7 −1.59

TABLE 3 Tabulated organic solar cell data CN (v/v) V_(OC) (V) J_(SC) (mAcm⁻²) FF PCE 3% 1.03 8.53 0.35 3.03 5% 1.02 9.62 0.35 3.41 7% 1.00 8.440.34 2.90

Example 2: Synthetic Example

In a 5 mL pressure vial, IDT (0.025 g, 0.0245 mmol, 1 eq), PDI precursorNPDI-Br (0.075 mg, 0.106 mmol, 4.2 eq), SiliaCat® DPP-Pd (5 mol % Pd),pivalic acid (PivOH, 30 mol % with respect to IDT core), and potassiumcarbonate (0.015 g, 0.0109 mmol, 4.5 eq.) were added with a stir barfollowed by the addition of anhydrous N,N′-dimethylacetamide (1 mL)solvent. The reaction mixture was sealed with a Teflon® cap under N₂ andheated at 120° C. in a LabArmor® bead bath for 24 hours. After 24 hours,the reaction mixture was poured into acetone (50 mL) and stirredovernight. The precipitated product was collected by filtration and thefiltrate was discarded. The solid product was subsequently dissolved indichloromethane and passed through a short neutral alumina plug toremove the silica-supported catalyst and any remaining inorganics. Uponremoval of solvent, the resulting material was sonicated in EtOAc (ethylacetate, 50 mL) before allowing it to stir at reflux for several hours.The resulting solution was allowed to cool to room temperature and theresulting material was subsequently filtered washing with EtOAc followedby acetone and isolated as a dark red powder yielding the desiredproduct in 62% yield (0.055 g, 0.0156 mmol, 62% yield). It is believedthat a small amount of tris-substituted compound was removed with theethyl acetate washing procedure.

Example 3: Synthetic Example

Into a 250 mL Schlenk flask, add 3,3′,5,5′-Br4Th2 (2.0 g, 4.16 mmol) anda stir-bar. Seal the flask with a new septum and complete three vacuumpurge+N₂-backfill cycles on a Schlenk line. Once filled with N₂, closeoff the Schlenk line and disconnect. Cannula transfer dried THF (80 mL)into the Schlenk flask. Stir to dissolve 3,3′,5,5′-Br4Th2 and then coolthe reaction mixture to −78° C. Add n-BuLi (3.7 mL, 9.2 mmol) dropwiseover 5 mins. Allow reaction mixture to stir for 1 hour. Add TMS-C1 (2.5eq.) dropwise to the cooled solution. Allow reaction mixture to stirovernight. Cool the stirring reaction mixture (containing3,3′,5,5′-Br2TMS2Th2) to −78° C. Add nBuLi (4.0 mL, 9.8 mmol, 2.3 eq)for 5 mins. Allow reaction to stir for ˜1 hour. Add CuCl₂ (1.70 g, 12.6mmol, 3 eq) to the solution under a stream of N₂. Allow the reactionmixture to stir overnight. Quench the reaction with water (75 mL), thenextract using Et₂O (4×50 mL). Dry the Et₂O extracts over Na₂SO₄. Filteraway the drying agent, then concentrate the solvent by rotoevaporation.The resulting crude oil was purified by silica gel column chromatography(hexanes) to afford TMS4Th4 as a yellow solid (452 mg, 0.73 mmol, 35%).

Methods and materials for making precursors useful in this method can befound in Urieta-Mora et al. which is incorporated by reference herein inits entirety.

Into a 100 mL round-bottomed flash, dissolve TMS4Th4 (0.30 g, 0.48 mmol)in minimal CHCl₃. Add TFA dropwise (4.5 equivalents), stir for ˜15 mins,then quench the reaction by adding excess water. Extract the aqueousmixture with CHCl₃ (3×30 mL); wash these extracts with water (2×50 mL),and then dry organic extracts over Na₂SO₄. Filter the dried extractsthrough Celite and remove solvent under reduced pressure. Precipitateproduct Th4 from MeOH, and collect the resulting pale yellow solid byvacuum filtration (128 mg, 0.47 mmol, 98%).

Into a 10 mL microwave vial, add Th4 (1 eq., 32.8 mg, 0.10 mmol),Br-PDI—N-Hex (4.5 eq., 320 mg, 0.45 mmol), Cs₂CO₃ (5 eq., 163 mg, 0.50mmol), and SiliaCat-Pd-DPP (0.1 eq., 40 mg, 0.01 mmol) and a stir-bar.Seal the vial and purge with N₂ for 30 minutes. Dried dimethylacetamide(6 mL) was cannula transferred into the vial and the reaction mixturewas sparged with N₂ for an additional 15 minutes. Acetic acid (0.5 eq.,3 mg, 0.05 mmol) was injected into the reaction vial and then the vialwas placed in a 120° C. bead bath for 24 hours. The reaction mixture wasthen poured into methanol (150 mL), stirred for 1 hour, and vacuumfiltered. The resulting crude solid was dissolved in CHCl₃ and adheredto silica. The silica adhered compound was placed on top of more silicaand the plug was eluted using: i) Hexanes:Acetone (4:1), then ii) CHCl₃,and lastly iii) CHCl₃+5% MeOH. The CHCl₃ fraction was further purifiedby column chromatography using CHCl₃. After removing solvent underreduced pressure, the crimson red solid Th4PDI4 was precipitated inmethanol and collected by vacuum filtration. (187 mg, 0.07 mmol, 70%).

¹H NMR, and HR-Maldi-MS of the resultant product are consistent withTH4PDI4 of structure:

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We claim:
 1. An oligomeric PDI compound of formula:

wherein: m is an integer of 4-10; Y is S, Se or N—R₃, R₁ and R₂ are thesame or different and are each independently selected from alkyl groupshaving 1-30 carbon atoms; R₃ is the same as or different from R₁ and R₂and is selected from alkyl groups having 1-30 carbon atoms; CORE isselected from the group consisting of the moieties C1-C40:

wherein: each R₄ is independently selected from hydrogen, an alkyl grouphaving 1-30 carbon atoms, an alkoxy group having 1-30 carbon atoms, anoptionally-substituted aryl group, an optionally-substituted heteroarylgroup; each R₅ is independently selected from hydrogen, halogen, CN, analkyl group having 1-30 carbon atoms, an alkoxy group having 1-30 carbonatoms; each R₆ is independently selected from hydrogen, halogen, CN, anoptionally-substituted phenyl group, an optionally-substituted benzylgroup, an alkyl group having 1-30 carbon atoms and an alkoxy grouphaving 1-30 carbon atoms; each R₇ is independently selected fromhydrogen, halogen, CN, an optionally-substituted phenyl group, anoptionally-substituted benzyl group, an alkyl group having 1-30 carbonatoms and an alkoxy group having 1-30 carbon atoms; each R_(N) isselected from hydrogen, an alkyl group having 1-30 carbon atoms, an arylgroup and an arylalkyl group; and where optional substitution issubstitution with one or more halogen, CN, an alkyl group having 1-30carbon atoms, or an alkoxy group having 1-30 carbon atoms.
 2. Theoligomeric PDI compound of claim 1, wherein the CORE is:


3. The oligomeric PDI compound of claim 1, wherein the CORE is:

where each R₅ is independently selected from hydrogen, halogen, CN, analkyl group having 1-30 carbon atoms, and an alkoxy group having 1-30carbon atoms.
 4. The oligomeric PDI compound of claim 3, wherein each R₅is independently hydrogen or an alkyl group having 1-12 carbon atoms. 5.The oligomeric PDI compound of claim 1, wherein the CORE is:

and each R₆ is independently selected from hydrogen, halogen, CN, anoptionally-substituted phenyl group, an optionally-substituted benzylgroup, an alkyl group having 1-30 carbon atoms, and an alkoxy having1-30 carbon atoms.
 6. The oligomeric PDI compound of claim 5, wherein R₆is hydrogen or an alkyl group having 1-12 carbon atoms.
 7. A tetramericPDI compound of formula:

where: each R₄ is independently selected from H, an alkyl group having1-30 carbon atoms, an alkoxy group having 1-30 carbon atoms, anoptionally-substituted aryl group and an optionally-substitutedheteroaryl group, where optional substitution is substitution with oneor more halogen, CN, alkyl group having 1-30 carbon atoms or alkoxygroup having 1-30 carbon atoms; and PDI has formula:

where: Y is S, Se or N—R₃, R₁ and R₂ are the same or different and areeach independently selected from alkyl groups having 1-30 carbon atoms,and R₃ is the same or different from R₁ and R₂ and is selected fromalkyl groups having 1-30 carbon atoms.
 8. The tetramer of claim 7,wherein each R₄ is an optionally-substituted aryl group.
 9. The tetramerof claim 7, wherein each R₄ is an optionally-substituted phenyl group.10. An electronic device employing an electron acceptor, wherein theelectron acceptor is one or more PDI oligomeric compounds of claim 1.11. The device of claim 10, which is an organic solar cell, an organicthin film transistor or a redox flow battery.
 12. A method for making anoligomeric PDI compound which employs direct (hetero)arylation (DHA),wherein one or more equivalents of a PDI precursor are reacted with 1equivalent of a CORE precursor, where the CORE precursor has four ormore C—H bonds that are active for DHA.
 13. The method of claim 12,wherein four or more equivalents of the PDI precursor are reacted with 1equivalent of the CORE precursor.
 14. A method for making an oligomericPDI compound which employs direct (hetero)arylation (DHA), wherein oneor more equivalents of a PDI precursor are reacted with 1 equivalent ofa CORE precursor, where the CORE precursor has four or more C—H bondsthat are active for DHA, where the oligomeric compound is a compound ofclaim
 1. 15. The oligomeric PDI compound of claim 1, wherein R₁ and R₂are the same or different and are each independently selected from alkylgroups having 1-12 carbon atoms; and R₃ is the same as or different fromR₁ and R₂ and is selected from alkyl groups having 1-12 carbon atoms.16. The oligomeric PDI compound of claim 15, wherein each alkyl oralkoxy group has 1-12 carbon atoms.
 17. The oligomeric PDI compound ofclaim 7, wherein: each Y is —NR₃; each R₁ and R₂ are the same and areselected from alkyl groups having 3-12 carbon atoms; each R₃ is the sameas or different from R₁ and R₂ and is selected from alkyl groups having3-12 carbon atoms; and each R₄ is an optionally-substituted aryl groupor an optionally-substituted heteroaryl group.
 18. The oligomeric PDIcompound of claim 17, wherein: each R₃ is n-hexyl, each R₁ and each R₂are 3-pentyl, and each R₄ is 4-n-alkyl-substituted phenyl.
 19. Theoligomeric PDI compound of claim 5, wherein each R₆ is hydrogen.
 20. Theoligomeric PDI compound of claim 19, wherein: each Y is —NR₃; each R₁and R₂ are the same and are selected from alkyl groups having 3-12carbon atoms; and each R₃ is the same as or different from R₁ and R₂ andis selected from alkyl groups having 3-12 carbon atoms.
 21. Theoligomeric PDI compound of claim 20, wherein: each R₃ is n-hexyl, eachR₁ is 3-pentyl and each R₂ is 3-pentyl.
 22. The oligomeric PDI compoundof claim 1 of formula:


23. The oligomeric PDI compound of claim 22, wherein: each Y is —NR₃;each R₁ and R₂ are the same and are selected from alkyl groups having3-12 carbon atoms; each R₃ is the same as or different from R₁ and R₂and is selected from alkyl groups having 3-12 carbon atoms; and each R₄is an optionally-substituted aryl group or an optionally-substitutedheteroaryl group.
 24. The oligomeric PDI compound of claim 23, wherein:each R₃ is n-hexyl, each R₁ and each R₂ are 3-pentyl, and each R₄ is4-n-alkyl-substituted phenyl.
 25. An electronic device employing anelectron acceptor, wherein the electron acceptor is one or more PDIoligomeric compounds of claim
 1. 26. An electronic device employing anelectron acceptor, wherein the electron acceptor is one or more PDIoligomeric compounds of claim
 5. 27. An electronic device employing anelectron acceptor, wherein the electron acceptor is one or more PDIoligomeric compounds of claim
 7. 28. An electronic device employing anelectron acceptor, wherein the electron acceptor is one or more PDIoligomeric compounds of claim 22.